Loud speaker



Een 233; 1926.;

F. J. REICHMANN LOUD SPEAKER Filed May 22, 1924 3 Shee'cssheet 1 F. J. REIQHMANN LOUD SPEAKER Fm 23 1926. LST/mm Filed May 22, 1924 5 Sheats-Sheet 5 /r/:an/T. @k/2761017 K lltD reame ree.. es, ieee,

RUUD SPEAKER.

'appagante aleen-ay sa, ieee. sanar nu, nenas,

To all 'whom it may concern ylie it known that l, FRANK d. REICH- MANN, a citizen of the United States, residing at Chicago, in the county of Cook and State of illinois, have invented certain new yand useful'lmprovements in a Loudv Speaker; and l do hereby declare the following to be a full, clear, and exact description ci? the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to telephonie rcceivers of the general class commonly employed as loud speakers in radio receiving apparatus and having an amplifying levery between thev electro-magnetically vibrated armature and the sound-producing diaphragin. lin sement its general aspects, it is theobject of my "invention to provide a telephonie receiver construction of this class arranged so that the parts can readily be assembled, .so that 'the needed adjustments can readily be made with an unusual deree of accuracyLso that the diaphragm will e in a neutral or untensioned position when no translatable current is ilowing,`so

that any later adjustments can be made with-y out detaching any part of the receiver or ,of its casing, and so that an unusually oliective amplification of sound can be obtained. Inl certain further aspects, my invention aims to provide 4a telephonie receiver employing two magnetic gaps splaced longitudinally of the permanent magne` associated therewith, aims to provide simple means for adjusting these gaps and so proportioning them as to aii'ord anefective distribution of lmagnetic liux between them', and aims to provide a telephonie receiver construction in which the magnetic gaps, can be adjusted with a high degree of accuracy before the ermanent magnet is placed in effective position. Furthermore, my invention aims to accomplish all of these results in a simple, Mcompact, easily manufactured, vconveniently assembled and inexpensive construction;

' Referrlng to 'some of the more particular aspects of my invention, it aims to provide a receiver construction which will require no drillingor ta ping of the' permanent inagnet, which w11 shdably lide thel energizing coil into aposition in which this coil' is properly disposed with Vrespect'to certain other parts, which will facilitate the assembly of the polepieces and which' will employ the polepieces :tor holding the energizing coil iirmly in its' normal position. lit also provides a construction in which the diaphragm is untensioned when the armature isin its'neutral position and in which the diaphragm is not subjected to any strains exerted in other directions than axial of the diaphragm, thereby permitting the eiiective use of such a highly desirable material as mica for -thediaphragm. lt also provides a simple and easily adjusted pair of control means for adjusting the normal or inoperative position of the lever which carries the armature, provides simple means for locking one ci these adjusting means, and provides means accessible from theexterior of the receiver for manipulating the other adjusting means, together with stopmeans for limiting the adjusting of the last named means.,

Furthermore, my invention provides an dit unusually rigid armature, pivot bar and stylus assembly, provides 'an' arrangement in which the armature has its medial plane inthe plane of the pivoting knife edges and of the neutral position of the diaphragm,

and provides-a' construction which will l readily permit this alinement to 'be obtained. Moreover, my invention provides a receiver construction in which both the pivoting knife edges and the sockets for thev adjusting 'l screws can be formed integral with the supporting body, and provides simple means upf on` the'pivot bar for preventing this from sliding lon itudinally of the knife edges. It also provi es an energizing coil construction which will reduce the `avera e distance Fig. 2 is a perspective view of a receiver some of. ,the features 0f the receiver of my 1nvention.

the axis of the adjusting screw 'which has the exposed knob.

Fig. 4 is. a perspective View of the same embodiment with the casing removed.

Fig. 5 is a top view of the same.

Fig. 6 is a bottom view, taken before the assembled mechanism is attached toV the permanent magnet and the bottom plate. Y'

Fig. 7 is a perspective view of the main supporting member, showing the pivoting knife edges, the guides for the spool carrying the energizing coil, and the threaded stems for receiving the polepieces and the iron blocks interposed between certain polepieces.

Fig. 8 is a perspective view of the main movable member of my receiver.

Fig. 9 is ay perspectiveview of the pivot-l ing cross-bar ofthis member before the armature, springs and diaphragm arm are attached to the same.

Fig. 10 is a perspective View of an alternativeform of pivoting cross-bar, namely one suitable for use with a single knife edge.

Fig. 11 is an end elevation of the telephonie 4receiver of Fig. 4, taken from the right hand end of that ligure.

Fig. 12 is a similar end elevation taken before attaching either the coil which carries the energizing spool, the interposed pole extensions, or the outer pair of polepieces.

Fig. 18 is a perspective view of the spool carrying the energizing coil,y

.Fig. 14 is a transverse section taken through the spool alone centrally of its length. A

Fig. 15 is a fragmentary transverse section through one of the iron blocks or pole extensions interposed between certain polepieces, taken along the correspondingly numbered line in Fig. 5.

Fig. 16 is a perspective view of one of the adjustable polepieces.

Fig. 17 is a perspective view of one of the pole extensions as interposed between the two polepieces adjacentto the same pole of the permanent horseshoe magnet.

In` accomplishing the purposes of my invention after the manner of the accompany- -ing drawings, I provide a receiver operating after the manner shown diagrammatically in Fig. 1, which ligure shows a diaphragm 1 connected by a diaphragm arm 2 to a pivoting cross-bar 3 which is pivoted on a knife edge 4. 'The pivot bar 3 has rigidly connected .to it an armature 5 extending in the opposite direction from the arm 2 through the bore of a. coil 6 which receives the energizing telephonie current. This armature 5 extends bet-Ween two pairs of invasie polepieces disposed respectively at opposite ends of the coil 6 and having each pole piece connected to that one of the other pair of polepieces which is disposed at 'the opposite side of the armature, the said polepieces being made of' soft iron and continuously polarized by means of a permanent magnet 7. -The armature is normally held in a neutral position between the two pairs of polepieces by pressure applied through two screws S and 9 to a pair of oppositely ydirected springs 10 and 11 secured to the pivot bar and extending in opposite directions from the pivot which is Vhere shown as a knife edge.

To secure both sensitiveness, clear articulation and high eiliciency from a receiver constructed after the manner of this diagram. it is highly important that the friction at the pivot be as small as possible, that the strains upon the diaphragm should be only along the direction of its axis, that this diaphragm should be in a. true neutral or untensioned position when no trans-- latabl energizing current is iiowing through the coil, that the turns of the coil should be as close as practical to the armature, that the magnetization of every one of the polepieces should be intense, and that the alrgaps between the armature and the polepieces should be as small 'as possible. Furthermore, it is important that simple means should be provided for overcoming the un balancing eifect due to any unidirectional flow of current through the energizing coil (such as that caused by the receiving tube of a`radio apparatus), that the needed adjustment for this purpose should readily be made initially by the manufacturer without materially increasing the friction at the pivot, and-that the user should lbe able to make a further adjustment of this kind according to the condition of the receiving tube and the battery employed by him. So also, it is important that the extent of the adjustments which can be made by a user for this purpose should be limited so as to prevent an inexperienced person 'from damaging the apparatus. Generally speak.

ing, I obtain these highly important requirements in the following manner To prevent side strains on the diaphragm, I place thepivoting axis of the main movable member (which axis is the edge of the 'knife edge 4 in Fig. 1) in the neutral plane 'invasie To insure the maximum sensitiveness of the diaphragm, l adjust the parts so that this diaphragm is in an untensioned ory neutral position when the armature is in its neutral position. For this purpose, l initially adjust the pressure screws 8 and 9 so that they will hold the pivoting bar 3 against the knife edge with a quite light pressure., and so that the oppositely directed eiiect of the two springs will 'have a balancing action tending tohold the armature in a properly centered position betweenboth pairs of poltpieces. Ylhen l apply further pressure through 1one of these screws to counteract the 'unbalaneing ei'il'ect of the direct current from the receiving tube, and for this purpose extend one ot these screws beyond-the easing so that this tube-dow-adjustment can be made from the exterior ofl the casing within limitations adorded by certain stops such as those hereafter described.

To secure an intense magnetic Hua between each pair ot polepieces, l connect these polepieces to the poles of a permanent,

magnet ot' much-larger cross-section and `provide a mounting which will enable each polepiece to be adjusted in position i n dependently et the otherathereby permit ting adjustments which will secure the minimum permissible argaps between the armature and the'tour polepieces. To permit the two'magnetic gaps to be spaced longitudinelly of the permanent magnet, in which case' one gap would afford a shorter magnetic circuit, l correspondingly increase the size of this gap so that it will not rob the other gap of a proper share of the magnetic hux, thereby ati'ordingV a strong magnetic action, at both gaps while having one of these quite small.

nthe magnetization of .the armature by a.

given How ot energizing current.` I also provide simple means for holding the coil in proper axial and rotational alinement with the neutral position of the armature, so as to permit the vemployment eta, coil having such a decidedly fiattened bore.

Furthermore, to expedite and simplify the manufacture, assembly and adjustment, y l provide a construction in which substantially all of the receiver vparts excepting the permancntzmagnet can be assembled and adjusted before attaching the permanent magnet to the sume, and in which ne work whatever will be required upon the magnet,

illustrative of such a construction, Fig. 3l shows a receiver embodying my invention and having a. permanent magnet 7 of a horseshoe type clamped between a bottom plate` 12 (desirably of brass) and an upper assembly which includes a supporting block 13 and a pair of magnet pole extensions 14 desirably are of brass) may be-out of contaetwith the magnet poles as` shown in Fig, 7.

The supporting block 13 may be et any non-magnetic material and is here shown as having a bore 18 extending downwardly into it and contracted at a distance' from its lower end so as to afford an annular shoulder 19 for supporting the lower one of the two cushioning rings 21 and 22 between which lilies-diaphragm is clamped by the attaching 'of a cover plate 23which isastened to the supporting block 13 by screws 24 as shown in Figs. 3 and 4. This supporting block -is shown also as having integral with it a pair of guideways 25 presenting opposed V-for-l mations which extend parallel to eachother and which have the apices of' the 'if-sectioned grooves in the same plane with a pair of knife edges '26 also milled Ifrom vthis block,

these knife edges in the illustrated embodimentbeing also substantially in the neutral plane of the diaphragm. The supporting block 13 may be widened at the end which has these guide formations and knife edges, so as to provideears 27 which afford relatively wide bearings for engagement with the adjustable polepieces. Projecting from these ears 27 parallel to the guideways 25 are threaded stems 28 for supporting the polepieces and the pole extensions. Each of the polepieces is here shown as comprising a soft iron punching formed after the manreo ner of Fig. 16 and comprising a ymain por tion provided with a pair of perforations 30 of considerably larger diameter than the screws 28, together with an arm 3l having l near its tip a straight-edged face spaced from the middle of the height of the block by a distance approximating one-half of the proposed average airgap between the two opposed polepieces. In assembling the polepieces, these are alternately inverted as shown in Figs. 11 and 12,50 that the said straight-edged faces can extend close to the opposed flat faces of the interposed arma- A 'ture 33.

Each of the polepieces has a pair of transy f shifted in position for adjusting airgap between it and the armature.

lin assembling my receiver, the movable member which includes the armature and its connection to the diaphragm is first attached to the supporting block 13. This movable member desirably includes apivoting cross bar 34: rigidly attached to the inner end of the armature and extending transversely of the lat-ter, and a diaphragm arm 35 also rigidly attached to the pivoting cross bar 34 and terminating in a perfor-ated bearing portion 3G which is riveted to the center ot the diaphragm 37. To provide for a rigid and j suitably alined assembly ot these three parts and the moving member, l desirably provide the pivoting cross bar with -a horizontal per- -iteration 38 by which the inner end of the arn'lature 33 is slidably received, and also provided with a vertical perforation 39 for similarly receiving one end ofv the diaphragm arm 35, and l neferably solder the inserted portions of the armature and the .diaphragm to the pivotingbar'when thus inserted.

To all'ord the pivoting, this cross bar is providedwith one or more tf-shaped grooves 40 according to the number of knife edges on the stationary supporting part which is here shown as the supporting block 13. Then l secure a pair of springs 41 and 42 to the opposite ends ot the pivoting bar, which springs extend in opposite direction, and desirably have end portions concaved towards the diaphragm. These end portions are perforated for receiving the shanks of adjusting lscrews 43 which are respectively threaded into lugs 45 on the supporting block 13. By slightly tightening both of these screws, l can readily hold the pivoting bar against the two knife edges on the supporting block with a relatively light pressure, and by adjusting these screws, I can dispose the armature so that its axls is in the same plane with groove bottoms of the guides 25, this being the determining -central plane of my energizing coil and polepiece desirably. WVhen the said screws are adjustedl so as to dis ose the armature in this position, the diap ragm arm 35 (which for this purpose is made of a bendable 'material) be bent so that its tip 36 jusb touches the untensioned diaphragm and is then riveted to the center of the diaphragm, thereby disposing its armature in itsl proposed neutral position when the diaphragm is also neutral or untensioned.

After the armature is thus initially positioned, I slide the two inner polepieces upon the threaded stems and fasten each thereinvasie on by means of nuts 46 as shown in Fig. 12 after adjusting the polepieces to provide the desired airgap betweenA them and the armature 33, this gap being sutliciently greater than the desired minute airgap between the outer polepieces so as to cause the proper proportion of the ux of the magnet to iiow through the outer pair of polepieces. l then slide the two pole extensions 14 and 15 upon the threaded stems into fiatwise engagement with the two inner polepieces as thus aiiixed, eac-h of these pole extensions having a pair ol" perforations i7 ot such size as to freely house the nuts 46 after the manner shown in Fig. 15. l also slide the assembled coiled spool i8 inwardly along the guides into-flatwise engagement with the inner pair ot polepieces, then slide the outer pair ot polepieces 49 on the threaded stems, adjust these as te their position with respect to the armature and secure them rigidly bv means oli' outer nuts 5l which also fit the threaded stems. rihese outer nuts cooperate with the threaded stems in serving. the triple `purpose of clamping the pole extensions ll and 15 against the inner polepieces o0, clamping the outer polepieces e!) against these pole extensionsa and elamp ing the adjacent end portions ot the outer polepieces against the outer face ot the coil spool 48, the latter having1 a length corresponding to the distance between the two pairs of .polepieces 'lo reduce the airgap between the windings on the energizing coil and the armature, l preferably provide the spool with a horizontally flattened tubular core 52 of only slightly larger height than the armature, thereby reducing the average distance between the turns of the coil and the 'armature as shown in Fig. 14 and hence increasing thel energy transforming eliiciency'ot' the coil. l also provide the two heads of the spool with oppositely directed 'il-shaped extensions 54 having a spread corresponding to the distance between the bottoms of the grooves in the guides 25, thereby causing the spool to be guided horizontally into position when slid between these guides and preventing movement of the spool and its coil in any direction other than axially of the coil, the movement in the axial direction being prevented by the clamping action of the two pair of fpolepieces between which the spool 1s gripped.

After the operating mechanism has thus been assembled in its adjusted and alined relation, the assembly is placed upon the permanent magnet 7 as shown in Fig. 4 and attached to the latter by`clam ing screws 16 and 17 which extend upward yfrom the bottom plate 12, thereby facing the pole extensions 14 and 15 firmly against the two poles of the permanent magnet. Since these clamping screws extend alongside the Shanks of themagnet,y no drilling or machining is required on the latter and the initial adjustments are made while the polepieces areI not even under any magnetizing influence, thereby per itting an accurate and quite delicate adjustment with a quite light tensioning ofthe two springs il and 42., However, when such a receiver is used in a radio apparatus in connection with a vacuum re,

ceiving tube, the constant current flowing through this tube will produce a corresponding unidirectional flow through the energizing coil 6, thereby tending to produce north and south poles respectively opposite the two pairs of polepieces and hence disturbing the magnetic'balance of the original adjustment. This can be compensated b-y a further regulation of one of the adjusting screws, but cannot be made permanently at the factory, as the volume of this unidirectional current will vary with the condition of the battery and of the tube. To allow for this, l extend one of the. adjusting screws so that it can be manipulated from outside the casing 52 in which my receiveris mounted, as by elongating the screw 44 and providing this with a knob 53. Then I also desirably attach a stop arm 5l to the extended screw 4:4: and provide the casing with a .p-air of stop pins 55 for limiting the adjustment'which can be made by the user, thereby preventing such an excessive movement of the screw as might interfere with the proper operation of my receiver.

By employing a. larger airgap between the inner polepieces than l do between the outer ones, l prevent the magnetic dax through the inner polepie'ces from robbing the outery ones of their proper share ot the ux, ot the permanent magnet, which robbing would result with a uniform spacing between the polep-ieces of both pairs since one` pair is closerto the pole ends of the magnet and hence would ai'ord a longer circuit for the magnetic dus. Hence l am able to employ' an. arrangement in which the pairsrof polepieces are spaced longitudinally ot' the magnet, thus utilizing a relatively larger and inexpensive permanent magnet. Furthermore, vsince no screws enter this magnet, it

- requires no machining such as would either reduce its permanent magnetization or wbuld require repeated heat treatments and re'magnetizing.

By providing an externally actuated adjustment, l adapt my receiver to eiectiveuse as part of a radio receiving set; and by limiting vthe extent of such adjustment, l avoid injury to the receiver by the recklessness of some amateur. However, l desir- =ably arrange fastening tor the 'adjusting knob so that this can bedetached. from, the threaded stem carrying the same and pan tially rotated beforeagain attaching the knob, thereby permitting any properly in- 'structed person to increase the range of adjustment over that ordinarily permitted by the limiting stops. For this purpose, l de sirabl rovide the knob with a square-sectionedy gore fitting a correspondingly' sectioned end portion of the threaded stem.

In practice, the bottom plate 12 is desirably rovided with an opening between the two sxlianks of the magnet so as to aord ready access to the mechanism and inspec tion of the same, and this bottom plate is here shown as secured to the base 56 of the casing by screws 57 However, l do not wish to be limited to the various details of construction and arrangement as here disclosed, it being obvious that many changes might be made without departing either from the spirit of my invention or from the appended claims. For example, Fig. l0 shows a pivoting bar diftering from that of Fig. v9 in -that it is provided with a single V-sectioned groove 58 for receiving a single knife edge, which knife edge desirably would correspondclosely in length to the groove so as to have its walls engaged by the latter to prevent'a shifting of the pivot bar along the knife edge. A. similar shifting would be prevented inthe ease of the pivot bar of Figs. 8 and 9 by the engagement of the adjacent ends of the two knife edges with the inner ends of the two pivot grooves 4&0. Nor do l wish to be limited tothe employment of all of the novel features of my invention in `its pivoting anis outside the coil and between the iaphragm and one ot the magnetic gaps, anda permanent magnet producing magnetic duXes across both gaps in respectively opposite directions.

2. A telephone receiver construction as per claim 1, in which the magnetic gap nearest to the pivot is greater than the one at the opposite end of the said coil.A

3. A telephone receiver construction as per claim. l, in which each magnetic gap is produced between a pair of polepieces, each of the polepieces being independently ad-' justable.

e. lin a telephonie receiver, an assembly comprising an armature movablev between two airs of polepieces and connected to a diap ragni, e. diaphragm casing, two magnet pole extensions secured to the said casing and each carrying one polepiece of each pair, and a permanent magnet clamped against this unit with its poles respectively hearing against the two magnet pole extensionsu 5. in a telephone receiver, a diaphragm, an energizing coil, an armature extending through the bore of the coil, a lever connecting the armature with the diaphragm and having its pivoting axis transverse of the axis of the coil and between the coil and the diaphragm, and means independent of the coi for producing two oppositely directed magnetic tiuxes transversely through the armature respectively between the coil and the said pivoting axis and at the other end of the coil.

6. A telephone receiver as per claim 5, in combination with separate means :tor adjusting the two magnetic iuxes into symmetry with respect to the axis of the coii.

7. ln a telephonic receiver, a permanent horseshoe magnet, a pair of pole extensions respectively engaging the two poles of the maget on the same face of the magnet, two pairs oi polepieces respectively secured to `the pole extensions and cooperating to ai- .iord two magnetic gaps spaced by dierent distances from the pole tips of the maget, and a pivoted armature extending through both magnetic gaps, the magnetic gap which is nearest to the pole tips being smaller than the other gap so as to reduce the shunting edect of the said other gap on the magnetic circuit.

t-. lin a telephonie receiver, a permanent horseshoe magnet, a pair of pole extensions respectively engaging the two poles of the magnet on the same 'ace of the magnet, two pairs oi polepieces respectively secured'to the pole extensions and cooperating to attford two magnetic gaps spaced by iieren't distances from the pole tips of the magnet, and a pivoted armature extending through both magnetic gaps, the ma etic ga which is nearest to the pole tips eing su eiently `smaller than the other gap to reduce the shunting effect of the latter on the magnetic circuit so as to substantially equalize the magnetic ux across the two gaps.

9. ln a telephone receiver of the type having a diaphragm connected to a pivoted armature, an energizing coil normally housing a part of the armature spaced from the pivot axis of the armature, and a permanent magnet having two pairs of polepieces adjacent to the armature and respectively at 'opposite ends of the spool, the airgap between the armature and the polepieces being larger for the pair nearest the pivot of the armature than for vthe other pair,

10. ln a telephonie receiver of the type having a pivotcd armature extending through two magnetic gaps spaced by an energizing coil through which the armature also extends, a diaphragm, a rigid conness Levanta armature of unidirectional current r'iow through the coii.

1l. A telephonie receiver as per claim l0, in combination with stop means for normally limiting the extent of the said adjustment.

l2. A. telephonie receiver comprising as a rigid unit a diaphragm casing, two pairs o' polepieces, two pole extensions disposed between the said pairs, an energizing coil disposed between the pole extensions; a pivoted member including an armature extending through the coil and between the polepieces of both pairs and a connection between the armature and the diaphragm; and yielding means for normally `holding the pivoted member in predetermined position; a permanent magnet supporting the above recited assembly of the rigid unit, the pivoted member an'd the spring means with the pole xtensions respectively engaging the poles of the magnet; a clamping plate supporting the magnet, and clamping members connecting the said unit with `the clamping plate to clamp the magnet therebetween.

13. A telephonie receiver as per claim 12, in combination with means supported by the said rigid unit for adjusting the said yielding .meanso la. A telephonie receiver as per claim l2, in combination with a casing housing all o vthe aforesaid and having a perforation, and

means extending through the casing and operable from outside the latter for adjust? ing the spring means.

15. ln a telephonic receiver, the combination with a diaphragm and a magnet spool, of a pivoted member; the said member comprising a pivoting bar having a socket ormation, a diaphragm arm fast upon the pivoting bar and extending transversely of the said bar, and connected to the diaphragm, and an armature extending 'through the bore of the magnet coil transversely of the said bar in the opposite direction from the diaphragm arm, thev armature having one end soclreted in the said socket formation.7

16. ln a telephonic receiver, the combination with a diaphragm of a pivoted member comprising a diaphragm arm and an armature extending transversely of and in opposite directions trom a pivoting bar, the armature and the diaphragm arm each having one end socketed in lthe pivoting baro 17. ln a telephone receiver', an energizing coil, two pairs et polepieces respectively disrevisie posed at opposite ends of the spool for affording two magnetic gaps in substantial alinement with the bore of the spool, a permanent magnet for polarizing all tour polepieces, and a pivoted armature extending through the here of the coil and having its pivoting axis outside the coil and in a plane axial or' the coil, loothl the armatureand the hore of the coil being,flattened/parallel to the said planee 18. lln a telephone receiver, an energizing coil having a flattened bore, ingly flattened armature extending through the bore ot' the coil, two pairs ot polepieees respectively disposed at oppositeends of the coil with the armature extending between the polepieces of each pair, a diaphragm, and a lever connecting the armature with the diaphragm and having its pivoting axis disposed in a plane parallel to the flattened bore walls.

19. lin a telephone receiver, a diaphragm, an armature connected thereto, two pairs of polepieces spaced longitudinally ot' the armature and having the armature extending hetween the polepieces of each pair, two soft iron blocks respectively clamped between the polepieces at each side of the armature, a mounting permitting separate adjustment of the positions of the polepieces, a permanent magnet having its poles normally respectively in engagement with the said blocks, and means external of the magnet for clamping the magnet in its said disposition.

20. A telephone receiver .as per claim 19, in which the clamping means include bolts threaded into the said blocksand extending alongside the poles of the permanent magnet,

21. ln a telephone receiver of the type in which an armature entends through a coil between magnetic gaps and is connected hy a lever to a diaphragm, a single-piece diaphragm casing and coil guide.

22.'ln a telephone receiver of the type in which an armature extends through a coil and between .magnetic gaps disposed at opposite ends of the coil and `is connected hy 'a lever to a diaphragm, a single-piece diaphragm casing and coil guide having lever- `pivoting, formations integral therewith.

23. ln a telephone receiver, an armature, a lever connecting the center of the diaphragm with the armature, a pair of guide w'ays extending at opposite sides of the armature and longitudinally of the armature, and an energizing coil member havingguides at diametrically opposite sides thereof titting the guideways to guide the' coil into axial alinement with the armature.

24. A telephone receiver as per claim 23, in which the energizing coil member includes alspool having heads fitting the guideways.

25. ln a telephone receiver, a magnet spool, pole pieces respectively engaging opa correspondposite ends of the spool to prevent longitudinal movement thereof, and spool supporting means-in which the spool is longitudinally insertable and which prevent lateral or rotational movement of the spool.

26. A receiver construction as per claim 25, in which the spool supporting means comprise plural guides extending longitudinally of the spool and in which the spool has formations at each end slidably engaging the said guides. n

27. lln a telephone receiver of Lthe type having a diaphraginconnected to a pivotcd armature, an energizing spool normally housing-part of the armature, a. permanent magnet, and movable polcpicces associated respectively with the poles of the magnet and respectively disposed at opposite ends of the spool and clamping the said spool cndwise between thema 28. ln a telephone receiver ot the type having a diaphragm connected to a pivoted armature, an energizing spool normally housing part of the armature, a support slidably receiving the spool in a disposition in which the-spool is coaxial with the neutral position of the armature, and polepieces clamping the spool between them.

29. ln a telephone receiver, an energizing coil, a pivoted armature extending through the coil; and a mounting tor the coil including a guide in which the coil is slidable longitudinally or" the armature, and means independent ot the guide for clamping the coil in a predetermined position, i

53th ln a -telephone receiver, an energizing coil, two pairs ot polepieces respectively at opposite ends of the coil, a pivoted armature extending through the coil and loetween the polepieces et each pair, and unitary supporting means for the said coil, polepieces and armature, the said supporting means being arranged to permit the attaching and adjusting of the armature before the polepieces and coil are placed in position 3l. ln a telephone receiver, an energizing coil, two pairs et polepieces respectively at opposite endsof the coil, a pivoted armature extending throughthe coil and hetween the polepieces of each pair, and unitary sup-` porting means for the said coil, pclepieces and armature, the said supporting means being arranged to permit the attaching and adjusting of the armature and one pair of polepieces before the coil and the other pair of polepieces are placed in position.

32. ln a telephone receiver, a lever com-l prising a medial pivotloar, and a diaphragm arm and an armature extending respectively :in opposite directions from, the pivot har, the pivot har extending transverse of the said arm and armature and having a groove extendingv longitudinally` thereof, and a stationary knife edge entering the said groove,

the groove having an end wall adapted to engage the ends of the knife edge to limit c the movement of the pivot bar longitudinally of the knife edge in one direction. 33. ln a telephone receiver, a lever comprising a medial pivot bar, and a diaphragm arm and an armature extending respectively in opposite directions from the pivot bar, the pivot bar extending transverse o the saidarin 'and armature and having a pair of alined grooves extending longitudinally thereof, and a pair'of stationary and alined knife edges respectively entering the said grooves, the tvvo grooves having relatively opposite end. wails each adapted to engage one end of the adjacent knife edges for preventing movement of the pivot bar longitudinally of 4the knife edges in respectively opposite directions. i

having a pivoted armature extending through two magnetic gaps spaced by an energizing coil through which the armature also extends, a diaphragm, a rigid connection between the diaphragm and the armature, spring means for holding the armature yieldngl'y in balanced relation to the tive magnetic gaps when no current is iowing through the coil; a casing housing the aforesaid elements, and means extending through the casing and operable from outside the latter for adjusting the spring means to 34C. In a telephonie receiver of the type' Levanta compensate tor-the edect on the armature of unidirectional current iiow through the coil'.`

. 35'. A telephonie receiver as per claim 34, in combination with stop means for tial alinelnentwith the bore o` the spool,

a permanent magnet for polarizing all four pole pieces, and a p'ivoted armature extending through the bore of the coil and having its pivoting axis outside the coil and in a plane axial of the-coil.

.37. In a telephone receiver, an energizing coil, a flat armature extending through the bore of the coil, two pairs of pole pieces respectively disposed at. opposite ends of the coil With the armature extendingy flatwise between the pole pieces of each pair, a diaphragm, and a lever 'connecting the armature with the diaphragm and having its pivoting axis disposed -in a plane parallel to the latfaces o the armature.

Signed at Chicago, illinois, May 20th,

FRANK J. RECHMANN. 

